The golden rule: Do unto others what you wish done unto yourself.
If you hit someone, then you want to be hit, so if they hit you to satisfy your need to be hit, then you have to hit them back.
that results in both of you being dead.
"Do not throw stones if you live in a glass house"
We all live in glass houses. If we all don't throw stones then will there be any advancement in society/science/ anything?
no, we'll just be a bunch of quiet primatives.